The effective medium theory was used to examine 2 kinetic phenomena which were related to the aggregation of the Au atoms deposited on a hex-reconstructed Au(100) surface. The island density could be analyzed by using scaling arguments derived from kinetic equations based upon an assumed growth mechanism. The calculations suggested that the diffusion of an isolated adsorbed atom was 2-dimensional, the dimer was mobile, and the critical nucleus size was one. Scanning tunnelling microscopy had shown that the islands formed by the Au atoms were elongated rectangles, and their widths were so-say quantized. Since the second surface layer had square symmetry and the top layer was hexagonal, the rectangular shape of the islands was not obvious. It was suggested that this form appeared because the atoms in the surface layer below the island were unreconstructed (i.e., had reverted to a square symmetry during island formation), while the atoms in the island had an hexagonal structure. Kinetics favoured a 6-atom wide island. The diffusion of an atom along the long side of such an island was much faster than when the island-width differed from 6. The atoms which stuck to the long side of a 6-atom wide island were rapidly transported to its short side; adding to the length rather than to the width of the island. This transport was inefficient when the width differed from 6.

An Effective Medium Theory Study of Au Islands on the Au(100) Surface - Reconstruction, Adatom Diffusion and Island Formation. L.Bönig, S.Liu, H.Metiu: Surface Science, 1996, 365[1], 87-95